1. Field
The present invention concerns a device and method for controlling the state of an energy accumulator connected to a fluid system.
2. Brief Description of Related Developments
Aircraft are generally equipped with several hydraulic circuits, a main one and at least one auxiliary one, independent and self contained, which permit the actuation of all the aircraft equipment. FIG. 1 depicts schematically such a hydraulic circuit for controlling a flap 1. This closed hydraulic circuit has a fluid reservoir 2 connected by a distribution circuit 3 to a hydraulic actuator 4. Such a distribution circuit 3 comprises rigid pipes and possibly flexible pipes for the mobile connections (brakes, landing gear, etc). The generation of hydraulic power is provided for example by a variable-output piston pump 5.
When the pilot acts on a control 6 such as a joystick, a control signal is sent to a computer 7 that controls a selector 8. In FIG. 1, the selector 8 is in the “retracted” position. One face of this actuator 4 receives the hydraulic pressure in an inlet chamber 9 causing a movement of the actuator towards the right. The flap 1 then moves downwards. The outlet chamber 10 of this actuator being connected in return to the reservoir 2, the fluid present in this chamber 10 is sent to the reservoir 2. A transmitter 11 sends a status signal for the flap 1 to the computer 7 for display 12. Naturally, the selector 8 can send the fluid under high pressure to the chamber 9 or to the chamber 10 according to the required direction of movement of the flap 1, downwards or upwards.
It is known that, in order to function effectively, the consumers 4 need a constant nominal pressure in the chambers 9 or 10 according to the manoeuvre to be performed. Rapid manoeuvres then make the nominal pressure drop transiently since the hydraulic pumps are no longer in a position to ensure the maintenance of this pressure, particularly if the consumers 4 are situated far from this pressure source. The fluid entering the inlet chamber 9 must in fact be under nominal pressure in order to make the flap 1 move in an optimum fashion. The fluid at low pressure being in the outlet chamber 10 returns via a low-pressure hydraulic line BP to the reservoir 2. It is this difference in pressure between the inlet 9 and outlet 10 chambers that actuate the flap 1.
An accumulator with an energy reserve 13 is then used, which will restore its hydraulic energy reserve to the consumer or consumers 4 in order to maintain the pressure at a level close to the nominal operating pressure. This accumulator with energy reserve 13 is placed on the high-pressure hydraulic line HP between the hydraulic power generator 5 and the consumers 4 furthest away from this power generator 5.
This accumulator 13 also makes it possible to absorb the overpressures generated in the hydraulic circuit by the functioning of the consumers 4. Damage to structure and equipment of the aircraft during an abrupt variation in pressure in the pipework is thus avoided.
An accumulator with energy reserve 13 comprises two cavities 14, 15 (FIG. 2). A first cavity 14 connected to a hydraulic circuit, and a second cavity 15 in which a gas is trapped under pressure. An elastic wall can be used to delimit these two volumes 14, 15. However, this elastic wall can lose efficacy through a prolonged contact with the fluid, the pressurised gas in the second cavity 15 then migrating in the fluid for example.
The correct functioning of this accumulator with energy reserve 13 is guaranteed only when the accumulator is correctly pressurised, it is necessary to regularly check the pressure of the gas present in the second cavity 15.
This operation is performed by a maintenance operator by means of a pressure gauge 16 for each of the hydraulic circuits of the aircraft. The immobilisation of aircraft on the ground, and the need to employ skilled personnel to perform these maintenance operations, gives rise to a significant cost for the airline.
Skilled operators are in fact necessary since, the pressure varying with temperature, erroneous pressure reading interpretations could arise.
In addition, these accumulators, which are placed inside the apparatus, require the use of supplementary means for transferring the point for reading the pressure of the gas present in the second cavity to a maintenance point situated on the external structure of the aircraft. This pipework, these pressure gauges and all the fixing means have an impact on the weight of the aircraft and therefore on its fuel consumption, and moreover impair the reliability of the accumulator with energy reserve and therefore of the hydraulic system on which the accumulator is mounted.
The objective of the present invention is therefore to propose a device and method for checking the pressurisation of an energy accumulator connected to a fluid system, simple in their design and in their operating method, economical and allowing particularly reliable, precise and automatic checking of the state of pressurisation of an energy accumulator.